Information on SIMS

The instrument used at the Analytical Instrumentation Facility, North Carolina State University, is a Cameca 3f with a proprietary CCD image storage system. The figure below gives you an impression of how this instrument looks like.

The following cross section might provide additional information on various system components of this instrument:

(1) Caesium ion source
(2) Duoplasmatron ion source
(3) Primary beam mass filter
(4) Immersion lens
(5) Specimen
(6) Specimen chamber
(7) Transfer optics
(8) Entrance Slit
(9) Electrostatic Analyzer
(10) Energy Slit
(11) Image transfer lens
(12) Spectrometer
(13) Electromagnet
(14) Final slit
(15) Projection lenses
(16) Projection, display and detection system
(17) Deflector
(18) Remote controlled faraday cup
(19) Electron multiplier
(20) Detection system

Specifications

Primary Gun

Duoplasmatron with a hollow cathode and an adjustable magnetic field.
Primary ions: O2+ Ar+ O-.
Acceleration potential: 5-17.5 kV.
Primary ion net energy: 0.5-17.5 keV.
Beam diameter: less than 3 micrometers to greater than 200 micrometers.
Ion current density on the sample: greater than 50 mA/cm^2 (probe diameter 50 micrometers, O2+), greater than 5 mA/cm^2 (probe diameter 50 micrometers, O-).
X-Y rastering: continuously variable from 0 to 500 micrometers.

Specimen stage and chamber

X and Y displacement by stepping motors or manual movement.
Reproducibility: +/- 1 micrometer.
Specimen dimensions: 25 mm in diameter - 13 mm thick.
Accessible area on the specimen 20x20 mm.
Rapid interchange of specimens via an airlock.
Direct viewing microscope.

Transfer optics

Three preset magnifications maximize the analytical sensitivity for the analyzed areas of 25, 150, and 400 micrometers in diameter.

Ion microscope (direct image)

Lateral resolution: 0.5 micrometers.
Field image: 25-400 micrometers in diameter.
Magnification: 50x to 2,000x.
Final image: 18 mm in diameter.
Binocular microscope for viewing the ion image.
35 mm camera for recording the ion image.

Mass spectrometer

Triple focusing.
Electrostatic sector: 90 degree angle; 86 mm radius.
Magnetic prism: 90 degree angle; 127 mm radius.
Ion energy transmission bandpass: variable from 1 to 130 eV.
Energy resolution: 1 eV.
Mass range: 1-280 amu (optional extension up to 500).
Mass resolution: 200-10,000.

Detectors

Dynamic range: 10^-19 A - 10^-9 A.
Faraday cup.
Electron multiplier.
Microchannel plate: Channel of 16 micrometers diameter with maximum gain of 10^3.
Fluorescent screen: 18 mm in diameter.

Vacuum system

Primary gun: turbomolecular pump 170 l/s.
Sample chamber: recirculating helium cryopump.
Airlock evacuated by turbomolecular pump.
Spectrometer: ion pump 80 l/s.
Detection chamber: ion pump 80 l/s.
Rotary pump: 12 m^3/hour.
Two ion gauges, two thermocouples, automatic control of vacuum system.

Automation

The instrument is operated by a specialized desk top computer. Software for the different analytical modes, such as mass spectra, depth profile, step scanning of sample, energy distributions, high resolution, and isotopic analysis, is provided.

Klaus G. Paul, 4-30-1994